Mechanical contactor



Filed Nov. 12, 1938 Y 2 Sheds-Sheet 1 f fi r l I 21 5 5 25 I o o o 14- 18 a m7 m4 Fig.1.

I? 15 16 16' 11 I? 15 15 F 14 7/ g -25 15 I i 21 f 19 L 7 g- 2 Fig 5;

WITNESSES: INVENTOR Gabriel Letsch.

ATTORNEY 06L 8, 1940. LETSCH 2,217,487

MECHANICAL CONTACTORV Filed Nov. 12, 1958 2 Sheets-Sheet 2 WITNESSES: INVENTOR Gabriel Lefsch.

ATTORNEY Patented Oct. 8, 1940 UNITED STATES PATENT OFFICE MECHANICAL CONTACTOR poration of Pennsylvania Application November 12, 1938, Serial No. 239,918 In Germany March 21, 1938 1 Claim.

The invention relates to rectifiers, and especially to polyphase mechanical rectifiers.

An object of the invention is to improve the mechanical operation that makes an electrical contact between the various contact sets in a mechanical rectifier.

Another object of the invention is to provide a mechanical rectifier assembly in which the contact sets are exposed for easy replacement without disturbance of the rest of the apparatus.

Another object of the invention is to provide a mechanical rectifier assembly that is easily and accurately adjustable in respect to the time of making contact through the various contact sets.

Other objects and advantages of the invention will be apparent from the following description and drawings, in which:

Figure l is a front view partly in elevation and partly in cross section of an embodiment of the invention,

Fig. 2 is an end elevational view partly in section of Fig. 1,

Figs. 3 and 4: are respectively a front and top 535 view partly in section of a modification of the invention, and

Figs. 5 and 6 are respectively front and top views partly in section of a still further modification of the invention.

30 he invention is an improvement in the mechanical operation of a polyphase mechanical rectifier system such as disclosed in the patent application of Erwin J anetschke, Serial No. 162,- 795, filed September '7, 1937, for Conversion sys- 35 terns, Eberhard Schutz, Serial No. 176,830, filed November 27, 1937, for Conversion systems, and Wilhelm Leukert, Serial No. 180,393, filed December 17, 1937, for Rectifier systems. Heretofore it was not possible to use such contact de- 40 vices for periodically switching on of heavy currents because the contacts were quickly damaged by the arcs so that the contacts became useless for operation in a comparatively short time. As explained in these applications however, the damage by reason of these arcs has been practically avoided by utilizing variable impedances having switching chokes l with iron cores connected in series with the contact sets.

These switching chokes I become abruptly saturated for a very small instantaneous value of current in the neighborhood of the zero point.

These variable impedances I produce a low current pause and at the same time delay the rise 55 of the return potential at the opening of the contacts by a shunt path 2 which is preferably capacitive and which is connected in parallel with the interrupting position. At the interrupting position, however, the choke coil l is actually in an unsaturated condition and, therefore, has an 5 impedance which is multiplied so that no reignition may take place. The exact setting of the opposite portions of the contacts and the predetermined contact path is important and is the subject matter of the present invention. 10

The invention contemplates that the structural units will be built up each of a contact segment with the associated drive transfer parts and auxiliary devices so that the parts are easily exchangeable and replaceable. Furthermore, the contact segments are symmetrically arranged, for example, as at the vertices of the regular polygon whereby the supervising of the rectifier operation is facilitated. Furthermore, a damaged contact set can be very quickly removed and the operation continued with a very short interruption.

In Figs. 1 through 6 three different modifications of the invention are illustrated. In all three modifications each of the six contact sets consist of two fixed contacts H and i2 with electrical connecting straps illustrated connected thereto. In addition to these fixed contacts II and I2,

'the contact sets include movable connecting conductors and a movable contact bridge 13. The stamp 25 which slides in a guiding bushing I4 is riveted against the action of the return spring it. The two fixed contacts, as well as" the guiding bushing, are fastened in the flange ll. The stamp it: has its own return spring it. In the device illustrated in Fig. l and the vertical section thereof represented in Fig. 2, the contact sets are arranged adjacent to each other along the drive shaft l9. Each contact set. is driven by a separate eccentric 20. The eccentrics are 40 displaced with reference to each other by 60. The base body 2! in which the shaft 19 is supported in bearings at a plurality of places has preferably the elongated longitudinal form 4 shown. The flanges carrying the contact sets are fastened in the upper side of the base body so that the contacts are easily accessible. A stirrup 22 of U shaped iron is fastened to the base body and operates as a base for the springs I6 to press against the contact bridge 13. On one end of the base body is the stator of a synchronous driving motor 23. The end wall 2:! of the base body at the same time forms one of the bearing shields of the driving motor.

In Fig. 3 and the associated horizontal section of Fig. 4, only a single eccentric 20 is present. The contact sets are arranged in a star about this single eccentric. The counter bearing 22 for the contact spring [6 is preferably individual for each contact set and fastened to the flange l! by means of the bolts 35. Here also, a synchronous motor 23 with its stator is built on to the actual cylindrical base body 2! in which the shaft [9 is supported in a bearing. Fig. and associated Fig. 6 show a contact device in which the drive motor moves a reeling wreath 25 by means of an eccentric 2G. The six arms 26 of this reeling wreath 25 transfer the switching movement to the contact set located in the upper end of the base body 25. The reeling wreath 25 is held by a ball and socket joint 2'! having an outer part 28 which is slidably guided in a guiding tube 29 fastened to to housing. A spindle 3D and handwheel 3i lifts and drops the part 23 to vary the engagement time or the overlap time of the contacts. The most previous manner of operation may be adjusted for each loading condition by the variation of the synchronous position of the switching rythm with reference to the phase position of the feeding alternating potential. For the purpose of making possible the adjustment during the operation in a purely mechanical manner, it is preferable not to connect the base body rigidly with the motor stator but to make both rotatable relative to each other.

It will be noted that the invention discloses a polyphase mechanical rectifier assembly in which the contact sets are symmetrically arranged in respect to the drive shaft and in which the various parts that might be subject to damage or wear can be easily and rapidly replaced.

It is apparent that many modifications may be made in the form, number and arrangement of the various elements disclosed in the preferred embodiments of the invention. Accordingly, only such limitations are intended on the following claim as is necessitated by the prior art.

I claim as my invention:

In a polyphase rectifier system a polyphase mechanical contactor comprising a base member, a plurality of pairs of readily removable fixed contact elements carried in insulated relation to said base, a bridge member for each pair of contact elements, a reeling reel for controlling said bridge members and a motor driven eccentric for actuating said reeling reel and means for adjusting the reeling reel to determine the time interval that the bridge member is in contact with the fixed contacts.

GABRIEL LETSCH. 

